INTRODUCTION Fetus health is of high importance in pregnant women and exposure to secondhand smoke (SHS) endangers maternal and fetal health. Therefore, in this study we examined the prevalence of exposure to SHS in pregnant women at home and the related factors. METHODS This cross-sectional study was conducted with 255 pregnant women who were referred to the Isfahan health care center from July to September 2018. A questionnaire that was designed by the research team was applied to collect data about the participants' prevalence of exposure, attitude-emotional dimension, perceived susceptibility, perceived severity, and perceived barriers. The questionnaire used was self-administered. The validity and reliability of the questionnaire were confirmed by a panel of experts. Cronbach's alpha of attitude-emotional dimension, perceived susceptibility, perceived severity, and perceived barriers were also calculated as 0.81, 0.91, 0.92, and 0.89, respectively. Statistically significant differences were examined using chi-squared test and Mann-Whitney test. RESULTS We found that the prevalence of exposure to SHS in pregnant women was 23.1%. The age of the husband (p=0.041), education level of the smoking husband (p=0.005), the education level of the pregnant woman (p=0.002), employment status of husband (p=0.010), and whether the pregnancy was planned (p=0.010) had significant association with the participant prevalence of exposure to SHS. Thus, older age of husbands, lower education levels of husbands and wives, unwanted pregnancies, and unemployment of husbands resulted in higher exposure to SHS. The mean scores of knowledge and perceptions were lower in women exposed to smoke than in non-exposed women (p<0.05). CONCLUSIONS The rate of SHS exposure was high in pregnant women. The knowledge and perception scores of exposed women to SHS were lower than those of non-exposed women. Low levels of education of husbands and women, unemployment and higher age of husbands, and unwanted pregnancies were considered as health risk factors. Therefore, effective training programs should be designed to educate pregnant women and their husbands.